The present invention relates generally to fastening systems. In particular, the present invention relates to a screw for penetrating and securing a particle producing material or a bulge producing material to a base material.
In construction and remodeling the use of cement board and similar materials has become common. Such materials can be literally sheets of cement, or other similar materials. Cement board is used in a variety of construction and remodeling applications. For example, cement board is prevalent and most desirable as a substrate in the tiling industry. The cement board can also be used as a subsurface or substrate for marble slabs on floors, walls and ceilings. Whereas a substrate such as plywood is good on floors and countertops where there are no water sources, such as showers, sinks, or faucets, cement board is impervious to water. Cement board resists swelling, softening, and deteriorating when exposed to water. Should water somehow get onto the cement board (e.g., through leaking pipes, cracked tiles or improperly grouted tiles) the cement board will remain a solid subsurface.
Cement board has other desirable characteristics. Cement board is easy work with; it is easy to handle and cut into desired pieces. It is usually delivered to the end user as a board of concrete, usually in 4 by 5 foot sections. It could range anywhere from a half inch thick for floors to ¼ inch thick for walls. The cement board can lay right on top of an existing subsurface, and it resists shifting.; Cement board has sufficient strength and stiffness, in wet and dry conditions, to resist deformation. Cement board also provides desired shear bond strength to secure tile to the board. It is dimensionally stable, and freeze/thaw and fire resistant.
Cement boards are typically attached to other materials by screw fasteners. One problem that exists when inserting a screw into a cement board is that small cement particles break off the cement board. Cement boards are particle producing materials. Such particles can adversely effect the insertion of the screw into the concrete board. For example, particles may become wedged between the screw and the concrete board and cause to screw to enter the concrete board on an angle. Also, particles may become wedged between the head of the screw and the cement board, thereby preventing the screw from seating flush with the surface of the cement board. It is therefore desirable to provide as screw that can move to the surface of the concrete board particles produced during the insertion of the screw. It is also desirable to provide a screw that can seat flush with the cement board.
Moreover, it is important that screws used with cement boards, and similar materials, avoid the possibility of failure due to fastener pull-through. Fastener pull-through occurs when the screw penetrates the concrete board to a point where the head of the screw no longer provides sufficient clamping force between the cement board and the base material. Thus, it is also desirable to provide a screw that avoids fastener pull-through.
What is needed is a fastener adapted for use with a particle producing material, such as a cement board, where insertion of the fastener removes particles produced by the material, provides desired clamping force and avoids fastener pull-through, and seats flush to leave a smoother surface on the particle producing material.
In addition, the use of composite lumber or materials alternative to wood is becoming more common. Such alternative materials have many advantages over wood. The alternative materials are often stronger and more durable then even pressure treated lumber. Many materials also offer better resistance to moisture, corrosive substances, termites and other insects, and other environmental strains that often prove to be detrimental to wood. Materials alternative to wood are used to construct everything from cabinets to decks. Such alternative materials are made by various processes. For example, alternative material or composite lumber may be made by blending recycled plastic resins with sawdust and extruding the blended mixture into standard lumber sections.
A problem associated with composite lumber is that conventional screws may produce unwanted results. Particularly, insertion of a conventional screw can cause remnants or shavings to be cut, extruded, or otherwise removed from the hole made by the screw, or may cause an undesirable bulge on the surface of the materials. Composite lumber is a bulge and/or remnant producing material.
What is needed is a fastener adapted for use with a bulge and/or remnant producing material, such as composite lumber, where insertion of the fastener does not cause formation of a bulge or remnants on the surface of the material, such that the screw seats flush and leaves a smoother surface on the material.